Spin valve sensor having antiparallel (AP) pinned layer with high resistance and low coercivity

ABSTRACT

A spin valve sensor includes an antiparallel (AP) pinned layer that has first and second ferromagnetic layers separated by a thin coupling layer. The first ferromagnetic layer is exchange coupled to an antiferromagnetic pinning layer so that its magnetic moment is oriented in a first direction and the second ferromagnetic layer is exchange coupled to the first ferromagnetic layer with its magnetic moment oriented in a second direction that is antiparallel to the first direction. In the preferred embodiment the first ferromagnetic layer is cobalt iron niobium hafnium (CoFeNbHf) and the second ferromagnetic layer is cobalt (Co). With this arrangement the first ferromagnetic layer reduces current shunting and has a high coercivity so as to stabilize the pinning of the pinned layer. The cobalt (Co) of the second ferromagnetic layer enhances the spin valve effect by being adjacent to a nonmagnetic electrically conductive spacer layer which, in turn, is adjacent to a ferromagnetic free layer.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a spin valve sensor with an improvedantiparallel (AP) pinned layer and more particularly to an AP pinnedlayer that has reduced current shunting and lower coercivity.

2. Description of the Related Art

The heart of a computer is an assembly that is referred to as a magneticdisk drive. The magnetic disk drive includes a rotating magnetic disk,write and read heads that are suspended by a suspension arm above therotating disk and an actuator that swings the suspension arm to placethe read and write heads over selected circular tracks on the rotatingdisk. The read and write heads are directly mounted on a slider that hasan air bearing surface (ABS). The suspension arm biases the slider intocontact with the surface of the disk when the disk is not rotating but,when the disk rotates, air is swirled by the rotating disk adjacent theABS to cause the slider to ride on an air bearing a slight distance fromthe surface of the rotating disk. When the slider rides on the airbearing the write and read heads are employed for writing magneticimpressions to and reading magnetic impressions from the rotating disk.The read and write heads are connected to processing circuitry thatoperates according to a computer program to implement the writing andreading functions.

The write head includes a coil layer embedded in first, second and thirdinsulation layers (insulation stack), the insulation stack beingsandwiched between first and second pole piece layers. A gap is formedbetween the first and second pole piece layers by a gap layer at an airbearing surface (ABS) of the write head. The pole piece layers areconnected at a back gap. Current conducted to the coil layer induces amagnetic field across the gap between the pole pieces. This fieldfringes across the gap at the ABS for the purpose of writing theaforementioned magnetic impression in tracks on moving media, such as incircular tracks on the aforementioned rotating disk.

In recent read heads a spin valve sensor is employed for sensingmagnetic fields from the rotating magnetic disk. The sensor includes anonmagnetic conductive layer, hereinafter referred to as a spacer layer,sandwiched between first and second ferromagnetic layers, hereinafterreferred to as a pinned layer, and a free layer. First and second leadsare connected to the spin valve sensor for conducting a sense currenttherethrough. The magnetization of the pinned layer is pinnedperpendicular to an air bearing surface (ABS) of the head and themagnetic moment of the free layer is located parallel to the ABS butfree to rotate in response to external magnetic fields. Themagnetization of the pinned layer is typically pinned by exchangecoupling with an antiferromagnetic layer.

The thickness of the spacer layer is chosen to be less than the meanfree path of conduction electrons through the sensor. With thisarrangement, a portion of the conduction electrons is scattered by theinterfaces of the spacer layer with the pinned and free layers. When themagnetizations of the pinned and free layers are parallel with respectto one another, scattering is minimal and when the magnetizations of thepinned and free layers are antiparallel, scattering is maximized.Changes in scattering alter the resistance of the spin valve sensor inproportion to cos θ, where θ is the angle between the magnetizations ofthe pinned and free layers. In a read mode the resistance of the spinvalve sensor changes proportionally to the magnitudes of the magneticfields from the rotating disk. When a sense current is conducted throughthe spin valve sensor, resistance changes cause potential changes thatare detected and processed as playback signals.

A spin valve sensor is characterized by a magnetoresistive (MR)coefficient that is substantially higher than the MR coefficient of ananisotropic magnetoresistive (AMR) sensor. For this reason a spin valvesensor is sometimes referred to as a giant magnetoresistive (GMR)sensor. When a spin valve sensor employs a single pinned layer it isreferred to as a simple spin valve. A spin valve is also know as a topor bottom spin valve depending upon whether the pinning layer is at thetop (formed after the free layer) or at the bottom (before the freelayer). A pinning layer in a bottom spin valve is typically made ofnickel oxide (NiO).

Another type of spin valve sensor is an antiparallel (AP) spin valvesensor. The AP pinned spin valve sensor differs from the simple spinvalve sensor, described above, in that the pinned layer of the AP pinnedspin valve sensor comprises multiple thin layers, which are collectivelyreferred to as an antiparallel (AP) pinned layer. The AP pinned layerhas a ruthenium (Ru) spacer layer sandwiched between first and secondferromagnetic thin layers. The first ferromagnetic thin layer has itsmagnetic moment oriented in a first direction by exchange coupling tothe antiferromagnetic pinning layer. The second ferromagnetic thin layeris immediately adjacent to the free layer and is antiparallel coupled tothe first thin layer because of the minimal thickness (in the order of 8Å) of the spacer layer between the first and second ferromagnetic thinlayers. The magnetic moment of the second ferromagnetic thin layer isoriented in a second direction that is antiparallel to the direction ofthe magnetic moment of the first ferromagnetic layer.

The AP pinned layer is preferred over the single layer pinned layer. Themagnetic moments of the first and second layers of the AP pinned layersubtractively combine to provide a net pinning moment of the AP pinnedlayer. The direction of the net moment is determined by the thicker ofthe first and second thin layers. The thicknesses of the first andsecond thin layers are chosen to reduce the net moment. A reduced netmoment equates to a reduced demagnetization (demag) field from the APpinned layer. Since the antiferromagnetic exchange coupling is inverselyproportional to the net pinning moment, this increases exchange couplingbetween the first ferromagnetic film of the AP pinned layer and thepinning layer. The high exchange coupling promotes higher stability ofthe head. When the head encounters elevated thermal conditions caused byelectrostatic discharge (ESD) from an object or person, or by contactingan asperity on a magnetic disk, the blocking temperature (temperature atwhich magnetic spins of the layer can be easily moved by an appliedmagnetic field) of the antiferromagnetic layer can be exceeded,resulting in disorientation of its magnetic spins. The magnetic momentof the pinned layer is then no longer pinned in the desired direction. Areduced demag field also reduces the demag field imposed on the freelayer which promotes a symmetry of the read signal. The AP pinned spinvalve sensor is described in commonly assigned U.S. Pat. No. 5,465,185to Heim and Parkin which is incorporated by reference herein.

The first and second ferromagnetic layers of the AP pinned spin valvesensor are typically made of cobalt (Co). Unfortunately, cobalt has highcoercivity, high magnetostriction and low resistance. When the first andsecond ferromagnetic layers are formed they are sputtered deposited inthe presence of a magnetic field that is oriented perpendicular to theABS which sets the easy axis (e.a.) of the ferromagnetic filmsperpendicular to the ABS. During operation of the head the AP pinnedlayer is subjected to extraneous magnetic fields that have componentsparallel to the ABS, such as components of the write field. Theseextraneous fields, combined with heating of the pinning layer, can causethe pinning layer to lose its pinning strength (exchange coupling) andallow the magnetic moments of the ferromagnetic layers to switch frombeing perpendicular to the ABS to some other direction. If thecoercivity of the ferromagnetic films is higher than the exchange fieldthat urges the magnetic moments of the ferromagnetic layers back totheir original positions the magnetic moments of the ferromagneticlayers will remain in the wrong direction. This renders the read headinoperable.

Cobalt (Co) has a high negative magnetostriction. The negative signdetermines the direction of any stress induced anisotropy. When amagnetic head is lapped, which is a grinding process, nonuniformcompressive stresses occur in the layers of the sensor. Because of themagnetostriction and the stresses the cobalt (Co) ferromagnetic filmsacquire a stress induced anisotropy that is parallel to the ABS. This isthe wrong direction. The stress induced anisotropy may rotate themagnetic moment of the first and second ferromagnetic layers of the APpinned layer to some extent from perpendicular to the ABS in spite ofthe exchange coupling field tending to maintain the perpendicularposition. This condition can cause read signal asymmetry.

The low resistance of the cobalt (Co) ferromagnetic films of the APpinned layer causes a portion of the sense current to be shunted pastthe free and spacer layers. This causes a loss of read signal.

Efforts continue to increase the spin valve effect of GMR heads. Anincrease in the spin valve effect equates to higher bit density(bits/square inch of the rotating magnetic disk) read by the read head.Promoting read signal symmetry is also a consideration. This isaccomplished by reducing the magnetic influences on the free layer. Asearch still continues to lower the coercivity, substantially eliminatemagnetostriction and increase the resistance of some of the criticallayers of the spin valve sensor.

SUMMARY OF THE INVENTION

The present invention provides a material for the pinned layer that hashigher resistivity and lower coercivity than the cobalt (Co) materialtypically employed in the pinned layer. This material is selected fromthe group comprising cobalt iron niobium hafnium (CoFeNbHf), cobalt ironniobium (CoFeNb), cobalt iron hafnium (CoFeHf) and cobalt niobiumhafnium (CoNbHf) wherein the preferred atomic weight percentage ofCoNbHf is 87/11/2. The preferred material is cobalt iron niobium hafnium(CoFeNbHf). While cobalt (Co) has a resistivity of 10-12 ohms cm, cobaltiron niobium hafnium (CoFeNbHf), has a resistivity of 110 ohms cm.Further, while cobalt (Co) has a coercivity of 50-200 Oe, cobalt ironniobium hafnium (CoFeNbHf) has a coercivity of 5-10 Oe wherein theatomic weight percentages were 86.5/0.5/11/2.

As mentioned hereinabove, the AP pinned layer has first and secondferromagnetic layers separated by a very thin ruthenium (Ru) layer. Thefirst ferromagnetic layer is exchange coupled to the pinning layer withits magnetic moment oriented in a first direction and the secondferromagnetic layer is exchange coupled to the first ferromagnetic layerwith its magnetic moment oriented in a second direction antiparallel tothe first direction. In a preferred embodiment the first ferromagneticlayer is cobalt iron niobium hafnium (CoFeNbHf) and the secondferromagnetic layer is cobalt (Co). With this arrangement the firstferromagnetic layer will reduce current shunting and have a lowercoercivity to stabilize pinning of the pinned layer. Cobalt (Co) is apreferred material for the second ferromagnetic layer since it enhancesthe spin valve effect by being adjacent to the spacer layer. In somearrangements, however, it may be desirable for the second ferromagneticlayer to be cobalt iron niobium hafnium (CoFeNbHf).

In still other embodiments of the invention one or both of the first andsecond ferromagnetic layers may have first and second films where one ofthe films is cobalt (Co) and the other film is cobalt iron niobiumhafnium (CoFeNbHf). The invention is applicable to top or bottom spinvalve sensors. In a top spin valve sensor the pinned layer is pinned bya pinning layer at the top of the sensor (pinning layer is closer to thewrite head than the pinned layer) and in a bottom spin valve sensor thepinned layer is pinned by a pinning layer that is at the bottom of thesensor pinning layer is (further away from the write head than thepinned layer). In a bottom spin valve sensor nickel oxide (NiO) istypically employed for the pinning layer. In this type of sensor anickel iron (NiFc) interface layer is employed between the pinning layerand the pinned layer for the purpose of promoting exchange coupling.Still further, in some embodiments of the invention a spin valveenhancement layer is employed. The spin valve enhancement layer is avery thin layer of cobalt (Co), such as 10 Å, that is located betweenand interfaces each of the spacer layer and the pinned layer. Theinvention can also be employed for simple spin valve sensors where asingle pinned layer is employed.

An object of the present invention is to provide material for a pinnedlayer for a spin valve sensor that has higher resistivity and lowercoercivity than prior art materials employed for pinned layers.

Another object is to provide a spin valve sensor that has improvedpinned layer stability in the presence of extraneous fields.

A further object is to provide an AP pinned spin valve sensor wherein afirst ferromagnetic layer antiparallel coupled to the pinning layer hashigh resistivity and low coercivity and a second ferromagnetic layerinterfacing the spacer layer is cobalt (Co) for promoting a GMR effect.

Other objects and advantages of the invention will become apparent uponreading the following description taken together with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a planar view of an exemplary magnetic disk drive;

FIG. 2 is an end view of a slider with a magnetic head of the disk driveas seen in plane 2—2;

FIG. 3 is an elevation view of the magnetic disk drive wherein multipledisks and magnetic heads are employed;

FIG. 4 is an isometric illustration of an exemplary suspension systemfor supporting the slider and magnetic head;

FIG. 5 is an ABS view of the slider taken along plane 5—5 of FIG. 2;

FIG. 6 is a partial view of the slider and magnetic head as seen inplane 6—6 of FIG. 2;

FIG. 7 is a partial ABS view of the slider taken along plane 7—7 of FIG.6 to show the read and write elements of the magnetic head;

FIG. 8 is a view taken along plane 8—8 of FIG. 6 with all material abovethe write coil and write coil leads removed;

FIG. 9 is an isometric ABS illustration of a read sensor which employs aspin valve sensor of the present invention;

FIG. 10 is an isometric ABS illustration of a first investigated simplespin valve sensor;

FIG. 11 is an isometric ABS illustration of the present simple spinvalve sensor;

FIG. 12 is an isometric ABS illustration of a second investigated APpinned spin valve sensor;

FIG. 13 is an isometric ABS illustration of a first embodiment of an APpinned spin valve sensor of the present invention;

FIG. 14 is an isometric ABS illustration of a second embodiment of thepresent AP pinned spin valve sensor;

FIG. 15 is an isometric ABS illustration of a third embodiment of thepresent AP pinned spin valve sensor;

FIG. 16 is an isometric ABS illustration of a fourth embodiment of thepresent AP pinned spin valve sensor;

FIG. 17 is an isometric ABS illustration of a fifth embodiment of thepresent AP pinned spin valve sensor;

FIG. 18 is an isometric ABS illustration of a sixth embodiment of thepresent AP pinned spin valve sensor;

FIG. 19 is an isometric ABS illustration of a seventh embodiment of thepresent AP pinned spin valve sensor; and

FIG. 20 is an ABS illustration of a top simple spin valve sensoremploying the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Magnetic Disk Drive

Referring now to the drawings wherein like reference numerals designatelike or similar parts throughout the several views, FIGS. 1-3 illustratea magnetic disk drive 30. The drive 30 includes a spindle 32 thatsupports and rotates a magnetic disk 34. The spindle 32 is rotated by amotor 36 that is controlled by a motor controller 38. A combined readand write magnetic head 40 is mounted on a slider 42 that is supportedby a suspension 44 and actuator arm 46. A plurality of disks, slidersand suspensions may be employed in a large capacity direct accessstorage device (DASD) as shown in FIG. 3. The suspension 44 and actuatorarm 46 position the slider 42 so that the magnetic head 40 is in atransducing relationship with a surface of the magnetic disk 34. Whenthe disk 34 is rotated by the motor 36 the slider is supported on a thin(typically, 0.05 μm) cushion of air (air bearing) between the surface ofthe disk 34 and the air bearing surface (ABS) 48. The magnetic head 40may then be employed for writing information to multiple circular trackson the surface of the disk 34, as well as for reading informationtherefrom. Processing circuitry 50 exchanges signals, representing suchinformation, with the head 40, provides motor drive signals for rotatingthe magnetic disk 34, and provides control signals for moving the sliderto various tracks. In FIG. 4 the slider 42 is shown mounted to asuspension 44. The components described hereinabove may be mounted on aframe 54 of a housing 55, as shown in FIG. 3.

FIG. 5 is an ABS view of the slider 42 and the magnetic head 40. Theslider has a center rail 56 that supports the magnetic head 40, and siderails 58 and 60. The rails 56, 58 and 60 extend from a cross rail 62.With respect to rotation of the magnetic disk 34, the cross rail 62 isat a leading edge 64 of the slider and the magnetic head 40 is at atrailing edge 66 of the slider.

FIG. 6 is a side cross-sectional elevation view of the merged MR head40, which includes a write head portion 70 and a read head portion 72,the read head portion employing an AP pinned spin valve sensor 74 of thepresent invention. FIG. 7 is an ABS view of FIG. 6. The spin valvesensor 74 is sandwiched between first and second gap layers 76 and 78,and the gap layers are sandwiched between first and second shield layers80 and 82. In response to external magnetic fields, the resistance ofthe spin valve sensor 74 changes. A sense current Is conducted throughthe sensor causes these resistance changes to be manifested as potentialchanges. These potential changes are then processed as readback signalsby the processing circuitry 50 shown in FIG. 3.

The write head portion of the merged MR head includes a coil layer 84sandwiched between first and second insulation layers 86 and 88. A thirdinsulation layer 90 may be employed for planarizing the head toeliminate ripples in the second insulation layer caused by the coillayer 84. The first, second and third insulation layers arc referred toin the art as an “insulation stack”. The coil layer 84 and the first,second and third insulation layers 86, 88 and 90 are sandwiched betweenfirst and second pole piece layers 92 and 94. The first and second polepiece layers 92 and 94 are magnetically coupled at a back gap 96 andhave first and second pole tips 98 and 100 which are separated by awrite gap layer 102 at the ABS. As shown in FIGS. 2 and 4, first andsecond solder connections 104 and 106 connect leads from the spin valvesensor 74 to leads 112 and 114 on the suspension 44, and third andfourth solder connections 116 and 118 connect leads 120 and 122 from thecoil 84 (see FIG. 8) to leads 124 and 126 on the suspension. In a mergedhead the second shield 82 for the read head 72 also serves as a firstpole piece 92 for the write head 70. In a piggyback head these areseparate layers.

FIG. 9 is an isometric ABS illustration of the read head 72 shown inFIG. 6. The read head 72 has a spin valve sensor 130 which will bedescribed in more detail hereinafter. First and second hard bias andlead layers 134 and 136 are connected to first and second side edges 138and 140 of the spin valve sensor. This connection is known in the art asa contiguous junction and is fully described in commonly assigned U.S.Pat. No. 5,018,037 which is incorporated by reference herein. The firsthard bias and lead layers include a first hard bias layer 140 and afirst lead layer 142 and the second hard bias and lead layers 136include a second hard bias layer 144 and a second lead layer 146. Thehard bias layers 140 and 144 cause magnetic flux to extendlongitudinally through the spin valve sensor 130 for stabilizingmagnetic domains of the free layer. The spin valve sensor 130 and thefirst and second hard bias and lead layers 134 and 136 are locatedbetween nonmagnetic electrically insulative first and second read gaplayers 148 and 150. The first and second gap layers 148 and 150 are, inturn, located between first and second shield layers 152 and 154.

First Investigation of a Simple Spin Valve Sensor

FIG. 10 shows a simple spin valve sensor 160 which includes a spacerlayer (S) 162 of copper (Cu) between a pinned layer (P) 164 of cobalt(Co) and a free layer (F) 166 of nickel iron (NiFe). An interface layer168 of nickel iron (NiFe) may be located between the pinned layer 164and an antiferromagnetic (AFM) layer 170 of nickel oxide (NiO). The AFMlayer 170 pins the magnetic moment of the pinned layer 164 in adirection perpendicular to the ABS. The interface layer 168 is employedfor the purpose of promoting an exchange coupling between theantiferromagnetic layer 170 and the pinned layer 164. The free layer 166has a magnetic moment that is directed substantially parallel to the ABSand rotates in response to applied fields from a rotating magnetic diskat various angles relative to the pinned direction of the magneticmoment of the pinned layer 164. A capping layer of tantalum (Ta) 172 isshown on the free layer 166. The thicknesses of the layers are exemplaryand may be other thicknesses as desired. I have found that the cobaltpinned layer 164 has a low resistivity, in the order of 10 to 12 Ω cm,and a high coercivity (H_(c)) in the order of 50 to 200 Oe. It would bedesirable if the resistivity of the pinned layer could be increased toreduce sense current shunting and if the coercivity of the pinned layercould be decreased so as to stabilize the direction of the moment of thepinned layer 164.

Present Simple Spin Valve Sensor

The present simple spin valve sensor 180 includes a spacer layer (S) 182of copper (Cu) which is located between a pinned layer (P) 184 of cobaltiron niobium hafnium (CoFeNbHf) and a free layer (F) 186 of nickel iron.A giant magnetoresistive (GMR) enhancement layer 188 is located betweenthe pinned layer 184 and the spacer layer 182 for the purpose ofincreasing the spin valve effect. It has been found that the GMRenhancement layer 188 interfaces the spacer layer 182 withoutintermixing therewith. An interface layer 190 is located between anantiferromagnetic layer (AFM) 192 and the pinned layer 184. Theinterface layer 190 serves the same function as the interface layer 168in FIG. 10. The AFM layer 192 pins the magnetic moment of the interfacelayer 190 perpendicular to the ABS which, in turn, pins the magneticmoment of the pinned layer 184 perpendicular to the ABS. A capping layer194 is located on the free layer 186 for protecting the free layer 186from subsequent layers and subsequent processing steps. The cobalt ironniobium hafnium (CoFeNbHf) material employed for the pinned layer 184has a resistivity of 110 ohms cm and a coercivity (H_(c)) of 5 to 10 Oe.This resistivity is significantly higher than the resistivity of thecobalt layer 164 in FIG. 10 and shunts considerably less of the sensecurrent. Further, the significantly lower coercivity of 5 to 10 Oe, ascompared to 50 to 200 Oe for the pinned layer 164 in FIG. 10, results ina more stable pinning of the magnetic moment of the pinned layer 184.

Second Investigation of AP Pinned Spin Valve Sensor

FIG. 12 shows an AP pinned spin valve sensor 200 investigated by me. Thesensor 200 includes a spacer layer (S) 202 of copper (Cu) between an APpinned layer 204 and a free layer (F) 206 of nickel iron (NiFe). The APpinned layer 204 includes a ruthenium (Ru) layer 208 which is locatedbetween a first ferromagnetic layer 210 of cobalt and a secondferromagnetic layer 212 of cobalt. The thicknesses of each of the cobaltlayers 210 and 212 may be 24 Å and the thickness of the ruthenium layer208 may be 8 Å. An interface layer 214 of nickel iron (NiFe) is locatedbetween an antiferromagnetic layer (AFM) 216 of nickel oxide (NiO) andthe first cobalt layer 210 of the AP pinned layer. A capping layer 218is located on the free layer 206. The thicknesses of the layers shown inFIG. 12 are exemplary and may be changed as desired. I found that thefirst and second cobalt layers 210 and 212 exhibit low resistivity, inthe order of 10 to 12 ohms cm, and high coercivity (H_(c)), in the orderof 50 to 200 Oe. Accordingly, the cobalt layers 210 and 212 shunt asignificant amount of the sense current due to their low resistivity andcan be magnetically unstable due to a coercivity (H_(c)) in the range of50 to 200 Oe.

Various Embodiments of the Present AP Pinned Spin Valve Sensor

A first embodiment of the present AP pinned spin valve sensor 300 isshown in FIG. 13. The spin valve sensor 300 includes a spacer layer (S)302 of copper (Cu) which is located between an AP pinned layer 304 and afree layer (F) 306 of nickel iron (NiFe). The AP pinned layer 304includes a ruthenium (Ru) layer 308 which is located between a firstferromagnetic layer 310 of cobalt iron niobium hafnium (CoFeNbHf) and asecond ferromagnetic layer 312 of cobalt (Co). The ruthenium (Ru) layer308 may be 8 Å thick, the cobalt iron niobium hafnium (CoFeNbHf) layer310 may 35 Å thick and the cobalt (Co) layer 312 may be 24 Å thick. Thecobalt iron niobium hafnium (CoFeNbHf) material of the layer 310 has aresistivity which is significantly higher than the resistivity of thecobalt layer 210 in FIG. 12 and has a coercivity (H_(c)) which issignificantly lower than the coercivity of the cobalt layer 210 in FIG.12. Accordingly, the layer 310 shunts very little of the sense currentand is magnetically more stable than the cobalt layer 210 in FIG. 12.The cobalt layer 312 serves a double function, namely serving as apinned layer for scattering of conduction electrons upon rotation of thefree layer 306 and serving as a GMR enhancement layer because of itsinterfacing with the spacer layer 302, as discussed in regard to theembodiment 180 in FIG. 11. Accordingly, in the embodiment 300 in FIG. 13the cobalt iron niobium hafnium (CoFeNbHf) is employed for only one ofthe ferromagnetic pinned layers of the AP pinned layer 304. The APpinned spin valve sensor 300 in FIG. 13 further includes an interfacelayer 314 which is located between an antiferromagnetic (AFM) layer 316of nickel oxide (NiO). A capping layer 318 of tantalum (Ta) may beemployed on top of the free layer 306. Again, the thicknesses shown forthe various layers are exemplary and may be changed as desired.

A second embodiment of the present AP pinned spin valve sensor 400 isshown in FIG. 14. In this embodiment a spacer layer (S) 402 of copper(Cu) is located between an AP pinned layer 404 and a free layer (F) 406of nickel iron (NiFe). The AP pinned layer 404 includes a ruthenium (Ru)layer 408 which is located between first and second ferromagnetic layers410 and 412. The first ferromagnetic layer 410 includes a first film 414of cobalt iron niobium hafnium (CoFeNbHf) and a second film 416 ofcobalt (Co). The first film 414 may be 25 Å thick and the second film416 may be 5 Å thick. The second ferromagnetic layer 412 is cobalt (Co)and may be 24 Å thick. The cobalt layer 416 of the first ferromagneticlayer 410 provides an improved interfacing between the cobalt ironniobium hafnium (CoFeNbHo layer 414 and the ruthenium (Ru) layer 408.The cobalt iron niobium hafnium (CoFeNbHf) layer 414 reduces sensecurrent shunting in the first ferromagnetic layer 410 and increases themagnetic stability thereof. In the same manner as the cobalt layer 312in FIG. 13, the cobalt layer 412 in FIG. 14 serves a double function asa pinned layer and as an improved interface with the spacer layer (S)402 for increasing the GMR effect. All interface layer 418 of nickeliron (NiFe) is located between the antiferromagnetic (AFM) layer 420 andthe cobalt iron niobium hafnium (CoFeNbHf) film 414. A capping layer oftantalum (Ta) is located on the free layer (F) 406. The thicknessesshown for the various layers in FIG. 14 are exemplary and may be changedas desired.

A third embodiment of the present AP pinned spin valve sensor 500 isillustrated in FIG. 15. This embodiment includes a spacer layer (S) 502of copper (Cu) which is located between an AP pinned layer 504 and afree layer (F) 506 of nickel iron (NiFe). The AP pinned layer 504includes a ruthenium (Ru) layer 508 which is located between a cobaltiron niobium hafnium (CoFeNbHf) layer 510 and a second cobalt ironniobium hafnium (CoFeNbHf) layer 512. The ruthenium layer 508 is 8 Åthick, the first layer 510 is 35 Å thick and the second layer 512 is 35Å thick. The high resistivity of the first and second layers 510 and 512is the best embodiment of the AP pinned layer 504 for reducing sensecurrent shunting. Further, it is desirable to use the cobalt ironniobium hafnium (CoFeNbHf) material for both of the first and secondferromagnetic layers 510 and 512 of the AP pinned layer 504 foroptimizing the stability of the magnetic moments of the layers 510 and512. By employing the cobalt iron niobium hafnium (CoFeNbHf) materialfor the second ferromagnetic layer 512, a return of its magnetic momentto its original position is enabled in the same manner that the magneticmoment of the first ferromagnetic layer 510 is returned to its originalposition. Accordingly, in a preferred embodiment, cobalt iron niobiumhafnium (CoFeNbHf) is utilized in the layers on each side of theruthenium (Ru) layer 508. An interface layer 512 of nickel iron (NiFe)is employed between the antiferromagnetic (AFM) layer 514 and the cobaltiron niobium hafnium (CoFeNbHf) layer 510. A capping layer 516 islocated on the free layer (F) 506.

A fourth embodiment of the present AP pinned spin valve sensor 600 isillustrated in FIG. 16. This embodiment includes a spacer layer (S) 602of copper (Cu) located between an AP pinned layer 604 and a free layer(F) 606 of nickel iron (NiFe). The AP pinned layer 604 includes aruthenium layer (Ru) 608 which is located between a first ferromagneticlayer of cobalt iron niobium hafnium (CoFeNbHf) 610 and a secondferromagnetic layer of cobalt iron niobium hafnium (CoFeNbHf) 612. Thethickness of the ruthenium (Ru) layer may be 8 Å thick, the thickness ofthe first ferromagnetic layer 610 may be 35 Å thick and the thickness ofthe second ferromagnetic layer 612 may be 20 Å thick. This embodimenthas a similar advantage to the embodiment 500 shown in FIG. 15 in thatthe cobalt iron niobium hafnium (CoFeNbHf) material is used for both thefirst and second ferromagnetic layers 610 and 612 for reducing sensecurrent shunting and increasing the magnetic stability of both of thefirst and second ferromagnetic layers 610 and 612. In addition, however,a cobalt layer (Co) 614 is employed between the AP pinned layer 604 andthe spacer (S) layer 602. The cobalt layer 614 serves as a GMRenhancement layer in the same manner as the layer 312 in FIG. 13 and thelayer 412 in FIG. 14. An interface layer 616 of nickel iron (NiFe) islocated between an antiferromagnetic (AFM) layer 618 and the firstferromagnetic layer 610 of the AP pinned layer. A capping layer 620 islocated on the free layer (F) 606.

A fifth embodiment of the present AP pinned spin valve sensor 700 isshown in FIG. 17. This embodiment includes a spacer layer (S) 702 whichis located between an AP pinned layer 704 and a free layer (F) 706 ofnickel iron (NiFe). The AP pinned layer 704 includes a ruthenium (Ru)layer 708 between a first ferromagnetic layer 710 and a secondferromagnetic layer 712. The first ferromagnetic layer 710 includes afirst film 714 of cobalt iron niobium hafnium (CoFeNbHf) and a secondfilm 716 of cobalt (Co). The first film 714 may be 25 Å thick and thesecond film 716 may be 5 Å thick. The second ferromagnetic layer 712 ismade from cobalt iron niobium hafnium (CoFeNbHf) and may be 20 Å thick.The AP pinned layer 704 in FIG. 17 has the same advantages as the APpinned layer 604 in FIG. 16 regarding resistivity and coercivity.Further, the AP pinned layer 704 in FIG. 17 employs the second film 710of cobalt (Co) between the first film 714 and the ruthenium (Ru) layer708 because of its improved interfacing with each of the layers 714 and708. A GMR enhancement layer 718 of cobalt (Co), which may be 10 Åthick, is located between the AP pinned layer 704 and the spacer layer(S) 702. This cobalt layer 718 provides improved interfacing with thelayers 712 and 702 and increases the GMR effect. An interface layer 720of nickel iron (NiFe) is employed between the antiferromagnetic (AFM)layer 722 of nickel oxide (NiO) and the first film 714 of the AP pinnedlayer 704.

A sixth embodiment of the present AP pinned spin valve sensor 800 isshown in FIG. 18. This embodiment includes a spacer layer (S) of copper(Cu) 802 located between an AP pinned layer 804 and a free layer (F)layer 806 of nickel iron (NiFe). The pinned layer 804 includes aruthenium (Ru) layer 808 located between first and second ferromagneticlayers 810 and 812. The first ferromagnetic layer 810 may include afirst film 814 of cobalt iron niobium hafnium (CoFeNbHf) and a secondfilm of cobalt (Co). The film 814 may be 25 Å thick and the second film816 may be 5 Å thick. The second ferromagnetic layer 812 includes afirst film 818 of cobalt (Co) and a second film 820 of cobalt ironniobium hafnium (CoFeNbHf). The first film 818 may be 5 Å thick and thesecond film 820 may be 15 Å thick. The AP pinned layer 804 in FIG. 18has the advantage of high resistivity to prevent current shunting andlow coercivity to promote magnetic stability because of the cobalt ironniobium hafnium (CoFeNbHf) material employed for the films 814 and 820.The AP pinned layer 804 has a further advantage by employing films 816and 818 of cobalt (Co) on each side of the ruthenium (Ru) layer 808 forpromoting a better interface between the layers. A GMR enhancement layer822 of cobalt (Co) may be employed between the AP pinned layer 804 andthe spacer layer (S) 802 for enhancing the GMR effect. The thickness ofthis layer may be 10 A. An interface layer 824 of nickel iron (NiFc) isemployed between the antiferromagnetic (AFM) layer 826 and the firstfilm 814 of the AP pinned layer. A capping layer 828 of tantalum (Ta)may be employed on the free layer (F) 806. The thicknesses of the layersshown in FIG. 18 are exemplary and may be changed as desired.

A seventh embodiment of the present AP pinned spin valve sensor 900 isshown in FIG. 19. This sensor 900 differs from the sensors shown inFIGS. 13-18 in that the sensor in FIG. 19 is a top spin valve sensorwhereas the spin valve sensors in FIGS. 13-18 are bottom spin valvesensors. A top spin valve sensor has the pinning layer located at thetop whereas a bottom spin valve sensor has the pinning layer located atthe bottom. The embodiment in FIG. 19 includes a spacer layer (S) 902 ofcopper (Cu) which is located between an AP pinned layer 904 and a freelayer (F) 906 of nickel iron (NiFe). The AP pinned layer 904 includes aruthenium (Ru) layer 908 located between a cobalt iron niobium hafnium(CoFeNbHf) layer 910 and a cobalt iron niobium hafnium (CoFeNbHf) layer912. The AP pinned layer 904 in FIG. 19 will have the same advantages asthe pinned layer 504 in FIG. 15 by providing high resistivity to lessencurrent shunting and low coercivity to promote magnetic stability of theAP pinned layer. An antiferromagnetic layer (AFM) 914 of nickelmanganese (NiMn) is exchange coupled to the cobalt iron niobium hafnium(CoFeNbHf) layer 912 for pinning its magnetic moment perpendicular tothe ABS.

A tantalum layer 930 is located adjacent the antiferromagnetic (AFM)layer 914. The embodiment 900 is shown for the purpose of illustratingthat any one of the embodiments in FIGS. 13-18 may be a top spin valvesensor instead of a bottom spin valve sensor and still employ theconcepts of the present invention. The thicknesses shown for the variouslayers in FIG. 19 are exemplary and may be changed as desired.

An interface layer of cobalt (Co) 918 may be located between the AFMlayer 914 and the film 912 of the AP pinned layer for providing a betterexchange coupling between the layers 914 and 912. Accordingly, the AFMlayer 914 is exchange coupled to the interface layer 918 which is, inturn, exchange coupled to the layer 912. Further, interface layers 920and 922 of the AP pinned layer 904 may interface the ruthenium (Ru)layer 908 and the first and second cobalt iron niobium hafnium(CoFeNbHf) layers 910 and 912 for promoting exchange coupling betweenthese layers. GMR enhancement layers 924 and 926 may be employed forinterfacing the spacer layer 902 and a respective one of the free layer906 and the first ferromagnetic layer 910 of cobalt iron niobium hafnium(CoFeNbHf) 910 of the AP pinned layer.

An exemplary top simple spin valve 1000 is illustrated in FIG. 20wherein the antiferromagnetic layer (AFM) 1002 of nickel manganese(NiMn) is located at the top of the spin valve structure. A spacer layer1004 of copper (Cu) is located between a pinned layer (P) 1006 of cobaltiron niobium hafnium (CoFeNbHf) and a free layer (F) 1008 of nickel iron(NiFe). A GMR enhancement layer 1010 of cobalt (Co) may be employedbetween the free layer 1008 and the spacer layer 1004 for enhancing theGMR effect. An interface layer 1012 of cobalt (Co) may be employedbetween the AFM layer 1002 and the pinned layer 1006 for improving theexchange coupling between these layers and an interface layer 1014 ofcobalt (Co) may be employed between the pinned layer 1006 and the spacerlayer 1004. The thicknesses for the various layers shown in FIG. 20 areexemplary and may be changed as desired.

Alternatives of the Present Invention

Other materials that may be substituted for the cobalt iron niobiumhafnium (CoFeNbHf) material for the various layers described in FIGS. 11and 13-19 are cobalt niobium hafnium (CoNbHo), cobalt iron niobium(CoFeNb) and cobalt iron hafnium (CoFeHf). Other materials suitable forthe cobalt (Co) layers described in FIGS. 11 and 13-19 are cobalt iron(CoFe) and cobalt iron boron (CoFeB). The preferred atomic weightpercentages for the cobalt iron niobium hafnium (CoFeNbHf) material arc86.5/0.5/11/2. The nickel iron layers are preferably Ni₈₀Fe₂₀.

Clearly, other embodiments and modifications of this invention willoccur readily to those of ordinary skill in the art in view of theseteachings. For instance, the spin valve sensor may be employed forpurposes other than in a magnetic disk drive, such as a tape drivesearch and/or surveillance devices and laboratory equipment. Therefore,this invention is to be limited only by the following claims, whichinclude all such embodiments and modifications when viewed inconjunction with the above specification and the accompanying drawings.

I claim:
 1. A spin valve sensor comprising: an antiferromagnetic pinninglayer having magnetic spins oriented in a first direction; anantiparallel (AP) pinned layer which includes: first and secondferromagnetic layers wherein the first ferromagnetic layer is exchangecoupled to the pinning layer and has a magnetic moment pinned in a firstdirection by the pinning layer; a ruthenium spacer layer located betweenthe first and second ferromagnetic layers so that the secondferromagnetic layer has a magnetic moment that is pinned in a seconddirection that is antiparallel to said first direction; and at least oneof the first and second ferromagnetic layers being selected from thegroup comprising cobalt iron niobium hafnium (CoFeNbHf), cobalt ironniobium (CoFeNb), cobalt iron hafnium (CoFeHf) and cobalt niobiumhafnium (CoNbHf); a nonmagnetic electrically conductive spacer layer; aferromagnetic free layer that has a magnetic moment that is free torotate in response to applied fields; and the spacer layer being locatedbetween the AP pinned layer and the free layer.
 2. A spin valve sensoras claimed in claim 1 including: the pinning layer being nickel oxide(NiO); and an interface layer of nickel iron (NiFe) having first andsecond surfaces, the first surface being exchange coupled to the pinninglayer and the second surface being exchange coupled to the AP pinnedlayer.
 3. A spin valve sensor as claimed in claim 2 wherein said atleast one of said first and second ferromagnetic layers is cobalt ironniobium hafnium (CoFeNbHf).
 4. A spin valve sensor as claimed in claim 3wherein the second ferromagnetic layer is cobalt (Co).
 5. A spin valvesensor as claimed in claim 4 including: a giant magnetoresistive (GMR)enhancement layer of cobalt (Co); the GMR enhancement layer beinglocated between the AP pinned and spacer layers and interfacing thespacer layer.
 6. A spin valve sensor as claimed in claim 1 wherein: theantiferromagnetic layer is selected from the group comprising nickelmanganese (NiMn), platinum manganese (PtMn) and iridium manganese(IrMn).
 7. A spin valve sensor as claimed in claim 6 wherein said atleast one of said first and second ferromagnetic layers is cobalt ironniobium hafnium (CoFeNbHf).
 8. A magnetic head that has an air bearingsurface (ABS) comprising: a read head that includes: first and secondferromagnetic shield layers: first and second nonmagnetic electricallyinsulative gap layers located between the first and second ferromagneticshield layers; a spin valve sensor responsive to applied magneticfields; the spin valve sensor being located between the first and secondgap layers; and first and second electrically conductive lead layerslocated between the first and second gap layers and connected to thespin valve sensor for conducting a sense current through the spin valvesensor; the spin valve sensor including: an antiparallel (AP) pinnedlayer including first and second ferromagnetic layers and a ruthenium(Ru) layer wherein the ruthenium (Ru) layer is sandwiched between thefirst and second ferromagnetic layers; a pinning layer that has magneticspins oriented in a first predetermined direction that is perpendicularto the ABS; the AP pinned layer being exchange coupled to the pinninglayer with the first ferromagnetic layer interfacing the pinning layerso that a magnetic moment of the second ferromagnetic layer is pinned ina second predetermined direction that is antiparallel to said firstpredetermined direction; at least one of the first and secondferromagnetic layers being selected from the group comprising cobaltiron niobium hafnium (CoFeNbHf), cobalt iron niobium (CoFeNb), cobaltiron hafnium (CoFeHf) and cobalt niobium hafnium (CoNbHf); a free layerthat has a magnetic moment that is free to rotate relative to the secondpredetermined direction of the AP pinned layer in response to an appliedfield; a nonmagnetic electrically conductive first spacer layer; and thefirst spacer layer being located between the free layer and the APpinned layer.
 9. A magnetic head as claimed in claim 8 wherein thepinned layer is cobalt iron niobium hafnium (CoFeNbHf).
 10. A magnetichead as claimed in claim 9 including: a giant magnetoresistive (GMR)enhancement layer of cobalt (Co); the GMR enhancement layer beinglocated between the pinned and spacer layers and interfacing the spacerlayer.
 11. A magnetic head as claimed in claim 10 including: a writehead including: first and second pole piece layers and a write gaplayer; the first and second pole piece layers being separated by thewrite gap layer at the ABS and connected at a back gap that is recessedrearwardly in the head from the ABS; an insulation stack having at leastfirst and second insulation layers; at least one coil layer embedded inthe insulation stack; and the insulation stack and the at least one coillayer being located between the first and second pole piece layers. 12.A magnetic head as claimed in claim 11 including: the pinning layerbeing nickel oxide (NiO); and an interface layer of nickel iron (NiFe)having first and second surfaces, the first surface being exchangecoupled to the pinning layer and the second surface being exchangecoupled to the pinned layer.
 13. A magnetic head as claimed in claim 12wherein said at least one of said first and second ferromagnetic layersis cobalt iron niobium hafnium (CoFeNbHf).
 14. A magnetic head asclaimed in claim 13 wherein the second ferromagnetic layer is cobalt(Co).
 15. A magnetic head as claimed in claim 14 including: a giantmagnetoresistive (GMR) enhancement layer of cobalt (Co); the GMRenhancement layer being located between the pinned and spacer layers andinterfacing the spacer layer.
 16. A magnetic head as claimed in claim 12wherein: the first ferromagnetic layer includes first and second films,the first film being selected from said group and the second film beingcobalt (Co) and being located between the first film and the ruthenium(Ru) spacer layer, and the second ferromagnetic layer being cobalt (Co).17. A magnetic head as claimed in claim 16 wherein the first film iscobalt iron niobium hafnium (CoFeNbHf).
 18. A magnetic head as claimedin claim 17 including: a giant magnetoresistive (GMR) enhancement layerof cobalt (Co); the GMR enhancement layer being located between thepinned and spacer layers and interfacing the spacer layer.
 19. Amagnetic head as claimed in claim 11 wherein: the antiferromagneticlayer is selected from the group comprising nickel manganese (NiMn),platinum manganese (PtMn) and iridium manganese (IrMn).
 20. A magnetichead as claimed in claim 19 wherein said at least one of said first andsecond ferromagnetic layers is cobalt iron niobium hafnium (CoFeNbHf).21. A magnetic head as claimed in claim 20 wherein the secondferromagnetic layer is cobalt (Co).
 22. A magnetic head as claimed inclaim 21 including: a giant magnetoresistive (GMR) enhancement layer ofcobalt (Co); the GMR enhancement layer being located between the pinnedand spacer layers and interfacing the spacer layer.
 23. A magnetic diskdrive that includes at least one magnetic head that has an air bearingsurface (ABS), the disk drive comprising: the magnetic head including acombined read head and write head; the read head including: first andsecond ferromagnetic shield layers: first and second nonmagneticelectrically insulative gap layers located between the first and secondferromagnetic shield layers; a spin valve sensor responsive to appliedmagnetic fields; the spin valve sensor being located between the firstand second gap layers; and first and second electrically conductive leadlayers located between the first and second gap layers and connected tothe spin valve sensor for conducting a sense current through the spinvalve sensor; the spin valve sensor including: an antiparallel (AP)pinned layer including first and second ferromagnetic layers and aruthenium (Ru) layer wherein the ruthenium (Ru) layer is sandwichedbetween the first and second ferromagnetic layers; a pinning layer thathas magnetic spins oriented in a first predetermined direction that isperpendicular to the ABS; the AP pinned layer being exchange coupled tothe pinning layer with the first ferromagnetic layer interfacing thepinning layer so that a magnetic moment of the second ferromagneticlayer is pinned in a second predetermined direction that is antiparallelto said first predetermined direction; at least one of the first andsecond ferromagnetic layers being selected from the group comprisingcobalt iron niobium hafnium (CoFeNbHf), cobalt iron niobium (CoFeNb),cobalt iron hafnium (CoFeHf) and cobalt niobium hafnium (CoNbHf); a freelayer that has a magnetic moment that is free to rotate relative to thesecond predetermined direction of the AP pinned layer in response to anapplied field; a nonmagnetic electrically conductive first spacer layer;the first spacer layer being located between the free layer and the APpinned layer. the write head including: first and second pole piecelayers and a write gap layer; the first and second pole piece layersbeing separated by the write gap layer at the ABS and connected at aback gap that is recessed rearwardly in the head from the ABS; aninsulation stack having at least first and second insulation layers; atleast one coil layer embedded in the insulation stack; the insulationstack and the at least one coil layer being located between the firstand second pole piece layers; and the second shield layer and the firstpole piece layer being a common layer; a housing; a magnetic diskrotatably supported in the housing; a support mounted in the housing forsupporting the magnetic head with its ABS facing the magnetic disk sothat the magnetic head is in a transducing relationship with themagnetic disk; means for rotating the magnetic disk; positioning meansconnected to the support for moving the magnetic head to multiplepositions with respect to said magnetic disk; and processing meansconnected to the magnetic head, to the means for rotating the magneticdisk and to the positioning means for exchanging signals with the mergedmagnetic head, for controlling movement of the magnetic disk and forcontrolling the position of the magnetic head.
 24. A magnetic disk driveas claimed in claim 23 including: the pinning layer being nickel oxide(NiO); and an interface layer of nickel iron (NiFe) having first andsecond surfaces, the first surface being exchange coupled to the pinninglayer and the second surface being exchange coupled to the pinned layer.25. A magnetic disk drive as claimed in claim 24 wherein said at leastone of said first and second ferromagnetic layers is cobalt iron niobiumhafnium (CoFeNbHf).
 26. A magnetic disk drive as claimed in claim 25wherein the second ferromagnetic layer is cobalt (Co).
 27. A magneticdisk drive as claimed in claim 26 including: a giant magnetoresistive(GMR) enhancement layer of cobalt (Co); the GMR enhancement layer beinglocated between the pinned and spacer layers and interfacing the spacerlayer.
 28. A magnetic disk drive as claimed in claim 23 wherein: theantiferromagnetic layer is selected from the group comprising nickelmanganese (NiMn), platinum manganese (PtMn) and iridium manganese(IrMn).
 29. A magnetic disk drive as claimed in claim 28 wherein said atleast one of said first and second ferromagnetic layers is cobalt ironniobium hafnium (CoFeNbHf).
 30. A magnetic disk drive as claimed inclaim 29 wherein the second ferromagnetic layer is cobalt (Co).
 31. Amagnetic disk drive as claimed in claim 30 including: a giantmagnetoresistive (GMR) enhancement layer of cobalt (Co); the GMRenhancement layer being located between the pinned and spacer layers andinterfacing the spacer layer.
 32. A method of making a combined read andwrite head that has an air bearing surface (ABS) comprising: a making ofthe read head including: forming a ferromagnetic first shield layer;forming a nonmagnetic electrically insulative first gap layer on thefirst shield layer; forming a spin valve sensor on the first gap layeras follows: forming a pinning layer that has magnetic spins oriented ina first predetermined direction; forming an antiparallel (AP) pinnedlayer as follows: forming a first ferromagnetic layer on the pinninglayer with a magnetic moment pinned parallel to said first predetermineddirection; forming a film of ruthenium (Ru) on the first ferromagneticlayer; forming a second ferromagnetic layer on the ruthenium (Ru) layerthat has a magnetic moment pinned in a second predetermined directionthat is antiparallel to said first predetermined direction; selecting atleast one of the ferromagnetic layers from a group comprising cobaltiron niobium hafnium (CoFeNbHf), cobalt iron niobium (CoFeNb, cobaltiron hafnium (CoNbHf); forming a nonmagnetic electrically conductivefirst spacer layer on the second ferromagnetic layer of the AP pinnedlayer; forming a ferromagnetic free layer on the first spacer layer thathas a magnetic moment that is free to rotate relative to the secondpredetermined direction of the AP pinned layer in response to an appliedfield; forming first and second electrically conductive lead layers onthe first gap layer that are connected to the sensor; forming anonmagnetic electrically insulative second gap layer on the sensor, thelead layers and the first gap layer; and forming a ferromagnetic secondshield layer on the second gap layer; a making of the write headincluding:  forming a write gap layer and an insulation stack with acoil layer embedded therein on the second shield layer so that thesecond shield layer also functions as a first pole piece for the writehead; and  forming a second pole piece layer on the insulation stack andthe write gap and connected at a back gap to the first pole piece.
 33. Amethod as claimed in claim 32 including: the pinning layer being nickeloxide (NiO); and an interface layer of nickel iron (NiFe) having firstand second surfaces, the first surface being exchange coupled to thepinning layer and the second surface being exchange coupled to thepinned layer.
 34. A method as claimed in claim 33 wherein said at leastone of said first and second ferromagnetic layers is cobalt iron niobiumhafnium (CoFeNbHf).
 35. A method as claimed in claim 34 wherein thesecond ferromagnetic layer is cobalt (Co).
 36. A method as claimed inclaim 35 including: a giant magnetoresistive (GMR) enhancement layer ofcobalt (Co); the GMR enhancement layer being located between the pinnedand spacer layers and interfacing the spacer layer.
 37. A method asclaimed in claim 32 wherein: the antiferromagnetic layer is selectedfrom the group comprising nickel manganese (NiMn), platinum manganese(PtMn) and iridium manganese (IrMn).
 38. A method as claimed in claim 37wherein said at least one of said first and second ferromagnetic layersis cobalt iron niobium hafnium (CoFeNbHf).
 39. A method as claimed inclaim 38 wherein the second ferromagnetic layer is cobalt (Co).
 40. Amethod as claimed in claim 39 including: a giant magnetoresistive (GMR)enhancement layer of cobalt (Co); the GMR enhancement layer beinglocated between the pinned and spacer layers and interfacing the spacerlayer.